The present invention relates to a master cylinder, which is suitable for use in a clutch operating unit, a brake operating unit, or the like.
FIG. 26 is a cross sectional view showing one example of a master cylinder related to the present invention, which is disclosed in Japanese Patent Provisional Publication No. 10-53120. This master cylinder 1 has a piston 3 which is freely slidably fitted in a cylinder hole 2a formed in a cylinder body 2, and by the piston 3 and the cylinder body 2, a pressure generating chamber 4 and a hydraulic fluid waiting chamber 5 are sectioned. To the piston 3, a valve mechanism 6 and a throttle valve mechanism 7 are attached on the extension of the axis. In the valve mechanism 6, a flange 10 integrated with a rod 9 is separated from a circular member 11 to open an axial hole 12 as the piston 3 retreats to the restoration position by a return spring 8 provided in the pressure generating chamber 4, and the flange 10 comes into contact with the circular member 11 to close the axial hole 12 as the piston 3 advances from the restoration position.
Furthermore, the throttle valve mechanism 7 is equipped with a floating member 13 having a throttle hole 13a, and when there is a flow of hydraulic fluid running toward a reservoir through the axial hole 12 from the pressure generating chamber 4, it moves the floating member 13 to the throttled operating position where the throttling effect is exhibited to the flow of the hydraulic fluid, and when there is a flow of hydraulic fluid running toward the pressure generating chamber 4 through the axial hole 12 from the reservoir, it moves the floating member 13 to the unthrottled operating position where no throttling effect is exhibited to the flow of the hydraulic fluid.
Then, from the state where the valve mechanism 6 is open, the piston 3 operates, and it moves to the left in the figure and advances, so that the valve mechanism 6 may be closed, and the continuity between the pressure generating chamber 4 and the supplement passage 5 is cut off. After that, the piston 3 further moves to the left, and consequently, pressure is generated in the pressure generating chamber 4, and the hydraulic fluid is discharged from an output port 14. Until the valve mechanism 6 is closed after the start of advancing of the piston 3, the hydraulic fluid in the pressure generating chamber 4 escapes to the supplement passage 5 through the throttle valve mechanism 7 and the valve mechanism 6 by the advancing of the piston 3. By the flow of the hydraulic fluid at that moment, the floating member 13 of the throttle valve mechanism 7 closes a connecting hole 15a of a case 15. As a result of this, the hydraulic fluid in the pressure generating chamber 4 escapes to the supplement passage 5 through the throttle hole 13a of the floating member 13, so that the amount of the hydraulic fluid escaping to the supplement passage 5 from the pressure generating chamber 4 may be reduced when compared with that in the case when the flow of the hydraulic fluid escaping to the supplement passage 5 from the pressure generating chamber 4 is not throttled.
However, in the above master cylinder 1, a throttle valve mechanism 7 is provided on the extension of the axis of the piston 3, and therefore, there has been such a problem that the piston 3 becomes long, and the whole of the master cylinder 1 becomes large-sized, and the structure becomes complex, and the number of pieces of necessary parts is increased.
The present invention is made due to the above problems, and it is an object thereof to provide a master cylinder, in which the function of a throttle valve mechanism can be exhibited without making the whole of the master cylinder large-sized and the structure is simple and the number of pieces of parts can be reduced.
In order to attain the above object, the present invention provides a master cylinder, in which a piston is freely slidably provided in a cylinder hole formed in the cylinder body and by the above piston and the above cylinder body, a pressure generating chamber is sectioned, and a fluid passage for connecting the pressure generating chamber and a reservoir in order to supplement the hydraulic fluid to the pressure generating chamber is provided, and the hydraulic fluid pumped in the above pressure generating chamber when the piston operates is discharged to the output port, wherein a throttle passage which throttles the flow of the hydraulic fluid to the reservoir from the pressure generating chamber when the above piston operates is formed in the fluid passage, and a throttle valve mechanism which allows the hydraulic fluid to flow to the pressure generating chamber from the reservoir by opening a valve when the fluid pressure in the pressure generating chamber becomes lower than the pressure in the reservoir is provided in the fluid passage.
Furthermore, in the present invention, the throttle valve mechanism may be constituted by having a floating valve body, and a valve seat with and from which the floating valve body is brought into contact and is separated may be provided on the connecting portion to the cylinder body of the reservoir, and a fluid passage which supplements the hydraulic fluid to the pressure generating chamber from the reservoir when the valve of the throttle valve mechanism opens may be formed in either the throttle valve mechanism or the cylinder body, and a throttle passage can be provided in the fluid passage in parallel with the floating valve body, and the throttle valve mechanism may have a ball valve which performs opening and closing by the flow of the hydraulic fluid in the fluid passage and by its own weight and a throttle passage which is formed in parallel with the ball valve, and the ball valve may have a ball-shaped floating valve body; a valve seat with and from which the floating valve body is brought into contact and is separated; a slant face continuous with the valve seat and slanted in the direction in which the floating body rises when sitting, a waiting seat where the floating valve body is waiting apart from the valve seat when not operating; and a stopper which regulates a position where the floating valve body is waiting apart from the valve seat, and it is also possible that a circular piston guide is arranged around the periphery of the piston and the fluid passage is formed in the piston guide and a throttle passage which connects the fluid passages before and after the ball valve to make a detour is provided in the above piston guide.
Furthermore, the present invention provides a master cylinder, in which a piston is freely slidably provided in a cylinder hole formed in the cylinder body and by the piston and the cylinder body, a pressure generating chamber is sectioned and a fluid passage for connecting the pressure generating chamber and reservoir in order to supplement the hydraulic fluid is provided and the hydraulic fluid pumped in the pressure generating chamber when the piston operates is discharged to the output port, wherein a circular piston guide and a seal member may be arranged around the periphery of the piston and a circular chamber communicating with the reservoir may be constituted between the piston guide and the seal member and in the circular chamber, a circular floating valve body with a throttle passage for throttling the flow of the hydraulic fluid and a seating face with which the floating valve body comes into contact may be provided.
Also, the present invention provides a master cylinder, in which a cylindrical piston is freely slidably provided in a cylinder hole formed in the cylinder body and by the piston and the cylinder body, a pressure generating chamber is sectioned and a fluid passage for connecting the pressure generating chamber and reservoir in order to supplement the hydraulic fluid is provided and the hydraulic fluid pumped in the pressure generating chamber when the piston operates is discharged to the output port, wherein the throttle valve mechanism may be provided at a position of the fluid passage pierced in the peripheral wall of the piston and the throttle valve mechanism is equipped with a throttle valve portion which is brought into contact with and is separated from the fluid passage pierced in the peripheral wall of the piston on the inside surface side of the peripheral wall and which has a throttle passage, and a support portion which is fitted in the inside surface of the piston to support the throttle valve portion, and further, the throttle valve member which integrally has the throttle valve portion and the support portion may be fixedly fitted in the piston.
In the present invention, a throttle passage which throttles the flow of the hydraulic fluid to the reservoir from the pressure generating chamber when the piston operates is formed in the fluid passage, and a throttle valve mechanism which allows the hydraulic fluid to flow to the pressure chamber from the reservoir by opening the valve when the fluid pressure in the pressure generating chamber becomes lower than the pressure in the reservoir is provided in the fluid passage, and consequently, such effects that it is possible to exhibit the function of the throttle valve mechanism without making the whole of the master cylinder large-sized and that the structure is simple and the number of pieces of parts can be reduced and the cost can be decreased are attained. Furthermore, in the present invention, effects similar to the above effects can also be obtained in such a way in which a circular piston guide and a seal member are arranged around the periphery of the piston and a circular chamber communicating with the reservoir is constituted between the piston guide and the seal member and a circular floating valve body having a throttle passage for throttling the flow of the hydraulic fluid and a seating face with which the floating valve body comes into contact are provided in the circular chamber.
Furthermore, the throttle valve mechanism is provided at a position of the fluid passage pierced in the peripheral wall of the cylindrical piston, and the throttle valve mechanism has a throttle valve portion which is brought into contact with and is separated from the fluid passage pierced in the peripheral wall of the piston on the inside surface side of the peripheral wall and which has a throttle passage and a support portion which is fitted in the inside surface of the piston to support the throttle valve portion, and as a result of this, it is also possible to attain the reduction of the number of pieces of parts, cost cutting, and improvement of assembling efficiency using a simple structure, and the length of the piston does not become long so that it may be prevented from being oversized, and further, when starting to operate, the amount of the hydraulic fluid escaping to the reservoir accompanied with the advance of the piston can be reduced, and the pedal stroke of the brake or the like can be shortened, and when returning, the supplementation of the hydraulic fluid from the reservoir to the pressure generating chamber can smoothly be performed, and an effect of making the returning response good or the like can be obtained.